When you’re sitting in front of the Audio Research Reference 160S stereo amplifier ($22,000 USD), it’s hard not to see the appeal. Its GhostMeters are a brilliant design touch that modernizes the look of a metered power amplifier. So named because their needles appear at the front of an otherwise transparent pane of acrylic graduated in watts, the GhostMeters let the user simultaneously watch the needles dance along with the amp’s power output while peering past the meters to the glow of eight KT150 output tubes. Listening to music over a high-end stereo system can delight more than one sense -- if this sort of visual delight supports your pleasure in listening, then a plain ol’ slab of thick aluminum just won’t do.
Then, of course, there’s the sound . . .
Audio Research’s Reference series has long been considered audiophile royalty. The line’s name has become synonymous enough with High End that most audio aficionados refer to the models by “Ref,” followed by the model number -- just as Sylvester Stallone is simply Sly to insiders (or so I’ve read; I’m no insider). So although the name is Reference 160S -- the S denoting the stereo configuration -- Ref 160S is the common nickname.
In this model, ARC aims to make the lives of audiophiles who prefer tubes easy and stress free. The Ref 160S includes ARC’s proprietary auto-bias circuit -- no manual biasing of tubes needed -- as well as switchable balanced (XLR) and single-ended (RCA) inputs. A Triode/Ultralinear button on the front panel lets the user choose between those modes of operation: Triode produces a power output of about 70Wpc, Ultralinear the full 140Wpc of which this amp is capable. I settled on Ultralinear for my auditioning as I perceived the Ref 160S to sound a tad more dynamic in this mode, a little softer in Triode.
The 160S measures 19.0”W x 10.25”H x 21.5”D and weighs an even 100 pounds. Much of that weight is in the rear, where the transformers are mounted, concealed under a perforated black cover surmounted by the Audio Research logo. Sitting just behind the front panel are four matched pairs of KT150 output tubes, and between the KT150s and the transformers are two pairs of 6H30 tubes. Each KT150 tube is marked to correspond with a specific socket on the Ref 160S’s top deck -- no guesswork involved. When you’ve correctly inserted all 12 tubes -- a snap -- you’re basically done with setup. The KT150s are specified to last an estimated 3000 hours of use, the 6H30s 4000 hours. At an average of ten hours’ listening a week, that’s almost six years of steady use before the first KT150 might fail.
On the rear panel, in addition to the RCA and XLR jacks, are pairs of output binding posts labeled for 16-, 8-, or 4-ohm speakers -- for best sound, choose the impedance that most closely matches that of your speakers. There’s a 12V DC input with 3.5mm minijack for remote turn-on/off, an RS-232 connector, and an inlet for ARC’s stock, heavy-duty, 20A power cord. An Auto Shut Off/Defeat switch enables a tube-saving feature that powers down the Ref 160S after two hours with no signal present. That’s nice for peace of mind. The speed of the cooling fans is controlled with a High/Low switch. I left this set to Low, but never heard the fans come on during my time with the Ref 160S -- and I cranked it pretty high, sometimes just to show someone the meters dancing. An Hour Counter keeps a running total of the hours logged by the set of tubes installed. ARC suggests that you buy your replacement KT150s from them in sets of eight matched and tested tubes.
Centered on the front panel, below the meters, are four buttons: Power, Meter Light, Tube Monitor, and Ultralinear/Triode. Meter Light selects among four levels of front-panel brightness. Tube Monitor is used to check the status of the KT150 output tubes. Each tube has an LED -- four at far right of the front panel, four at far left -- that illuminates when that tube is functioning properly. Speaking of tubes operating correctly, the Ref 160S’s Auto Bias circuitry is ideal for those uninterested in tweaking tubes: Each time the Ref 160S is turned on, it automatically locks in the correct idle current for each quartet of KT150s, to ensure the best sound quality. KT120, KT88, or 6550WE output tubes can also be used, though ARC warns that both the sound quality and the output power will be adversely affected.
A large, silvery cage of perforated metal slides over tubes and transformer housing alike, to give the Ref 160S a clean if somewhat less interesting look, and to protect kids and pets from inadvertent contact with hot tubes. Handles front and rear -- the rear handles poke through tall slots in the back of the cage -- aid in moving the Ref 160S around. These were useful -- any 100-pound amp needs handles. I like the exterior design of the Ref 160S -- it exudes classic quality and solidity without rising to the level of audio jewelry. But those GhostMeters are supercool.
Like most power amps, the Ref 160S requires minimal setup. I placed it directly in front of my Boulder Amplifiers 2060 stereo amp, and changed over all connections other than the power cord (I used ARC’s stock cord). My MSB Technology Discrete DAC directly drove the 160S via balanced connection, and an Apple MacBook Air laptop computer running Roon and Qobuz fed the MSB. Loudspeakers were my references of the past couple years, Vimberg’s fantastic Tondas, and rounding out the system were Shunyata Research interconnects, speaker cables, and power conditioning, and an SGR Audio Model III Symphony rack. The Ref 160S was not persnickety, operating reliably throughout my listening for this review. It’s well engineered and thoughtfully designed.
I began my listening on a rainy Friday afternoon, cueing up on Qobuz one of my favorite bands of the last couple years: London Grammar. After just letting it play for about an hour, I began to notice that I really wasn’t noticing anything. True, I wasn’t listening at all that loud a volume, and my attention wasn’t intently focused on the sound -- but later, when I reflected on that session, it was suddenly obvious that the sound was unforced and easy to sink into -- just like that rainy Friday afternoon. I began to listen more intently to the super-quiet Ref 160S.
“Hell to the Liars” is from Truth Is a Beautiful Thing (16-bit/44.1kHz FLAC, Metal & Dust/Ministry of Sound/Qobuz), London Grammar’s second studio album. When Hannah Reid sings “Here’s to the things you love / Here’s to those you find in love / Hell to the rest of us,” I could easily hear every detail in her voice, the subtle reverberation after syllables, the changes in pitch as she sings notes lower in her range. The Ref 160S was tonally beyond reproach throughout the midband. If it’s true that “music lives in the midrange,” then the Ref 160S will bring your vocal recordings to life -- it did mine. I heard no colorations, just clear reproductions of singers’ voices -- and because that’s what London Grammar is mainly about, it served their music perfectly.
It’s at the extremes of the audioband that tube amps in general have gotten a bad rap, and some of them have deserved it. So I next dug into the highs, to hear what the Ref 160S could do with the upper registers. I played the Clarinet Concerto No.1 in B-flat Major (“Sant’ Angelo”) -- Andreas N. Tarkmann’s arrangement for solo clarinet and chamber orchestra of arias from Vivaldi’s operas and oratorios, and performed by soloist Martin Fröst and Concerto Köln (24/96 FLAC, Sony Classical/Qobuz). The sound of Fröst’s clarinet remained composed and fluid, sounding splendidly continuous and dense through the Ref 160S. The strings were delicate and easy to listen to, never grating or harsh, neither forced nor lacking in detail. It was all so easy to enjoy -- and I did.
Next I cranked it up with some Lady Gaga: her hit single “Rain On Me,” from Chromatica (24/48 FLAC, Interscope/Qobuz). This duet with Ariana Grande has a strong pop beat that, to sound right, demands a system that can deliver good midbass punch. The combination of the ARC Ref 160S and Vimberg Tonda speakers reproduced this track at peaks in excess of 90dB at my listening position, sounding terrific all the while. I heard no limitations in dynamics, and the midbass in particular had solid weight -- I could feel the punch in my body -- while Gaga’s and Grande’s voices sounded full, and filled my room. I wasn’t overdriving the system -- I didn’t want to push the limits of amp and speakers far enough to actually damage them -- but at 90dB the sound was effortless, with still more headroom than I could use. We’ve all heard that this sort of effortless quality inspires confidence in the ability of the components of a system. That’s what I felt.
On her latest release, This Dream of You, the voice and acoustic piano of Diana Krall sounded in-the-room real (24/44.1 FLAC, Verve/Qobuz). What occurred to me as I listened to this entire album was how three-dimensional the aural image of Krall sounded as it was projected before me. The tonality of her voice was far from artificial, with a great amount of detail, but what most struck me was the human-like shape and tangible depth of the center image. The image of Krall was dead center, about 3’ behind the plane described by the fronts of the speakers. I found that, through the Ref 160S, soundstages spread out evenly from side to side, and with impressive depth when the recording contained such information -- never exaggerated, always just right. You’ll enjoy exploring the soundstages of your favorite recordings through the Reference 160S.
At $22,900, Gryphon Audio Designs’ Essence stereo amplifier is close in price to the ARC Ref 160S’s 22 grand. Though to the casual observer these two products might seem to appeal to completely different potential buyers, I at first saw it as a classic faceoff of solid-state vs. tubes.
The two amplifiers have much in common. Each weighs about 100 pounds and is manufactured by a company with a stellar reputation. The ARC is the more powerful in terms of specs -- 140Wpc vs. 50Wpc into 8 ohms -- but I found those numbers more or less irrelevant in the context of my system and room. Both amps drove my speakers to loud levels with no clipping or compression that I could hear. Both also presented equally interesting appearances, and each is built to a high but not-over-the-top standard. But there’s another shoe to drop: their sounds.
The ARC Ref 160S didn’t have a stereotypically “tubey” sound -- that is, it wasn’t soft or truncated at the extremes of the audioband. Nor does the Gryphon Essence sound like a typical solid-state amplifier -- it’s not bright or harsh, nor does it display any of the other negative sound characteristics historically leveled against solid-state amps. However, I did hear some important differences, first and foremost in the bass. The Gryphon has more of it, and it’s stronger and more foundational, and lends music more gravitas -- but in these ways, the Essence is different from most other solid-state amps as well. Of course, the degree of this difference will depend on your speakers, your room, and the kind of music you play. If your speakers have powered bass sections or particularly full-sounding transducers, the advantage conferred by the Gryphon in this area may disappear. Perhaps surprisingly, I may have perceived the midrange of the Ref 160S as being a tad more neutral because of the Gryphon’s strengths in the lows, which can sometimes make its sound warm up into the midrange. The treble reproductions of the two amps were actually very close: both were excellent, and both could produce terrific detail in my system, beautifully resolving original recording venues, real or artificial, without ever sounding offensive.
This may sound a touch petty to some, but perhaps the biggest difference between these two amplifiers might come down to the audio worldview each represents -- and, thus, the audio worldview of anyone who might be attracted more to one than the other. Would you rather own a brute of a power amp, solid-state or tubed, from one of the most storied makers of either type? In other words, which speaks to you more, the Gryphon or the ARC? The differences in their sounds may or may not be enough to sway anyone one way or the other. It might just come down to a gut reaction to the overall experience of owning such a product. But either way, you’ll have a winner of an amp.
The Audio Research Reference 160S stereo amplifier is a solid bet. It has enough power not to limit your choice of speakers except in extreme circumstances. Its sound is neutral overall, but still gives you the luxury of tubes and none of the sonic drawbacks that tube aficionados can sometimes hear in solid-state amplifiers. It’s made by a company that, in my experience, stands behind its products. And though it’s pricey at $22,000, the Ref 160S is not ridiculously expensive for its qualities of sound and build.
And, let’s face it, those GhostMeters are beyond cool. If your idea of a good time is to turn the lights down, put on your favorite playlist, sip a good cup of coffee, and watch those meters bounce, backlit by the glow of that octet of KT150s, you’ve just planned out a really fine evening. Before I pack up the Reference 160S to send back to ARC, I think I’ll have another of those evenings myself.
. . . Jeff Fritz
- Speakers -- Vimberg Tonda
- Amplifier -- Boulder Amplifiers 2060
- DAC-preamplifier -- MSB Technology Discrete DAC
- Source -- Apple MacBook Air computer running Audirvana, Roon, Qobuz
- Interconnects, speaker cables, power cords -- Shunyata Research: Delta IC balanced interconnects, Alpha USB link, Alpha SP speaker cables, Venom NR-V10 power cords
- Power conditioner -- Shunyata Research Hydra Alpha A12
- Rack -- SGR Audio Model III Symphony
Audio Research Reference 160S Stereo Amplifier
Price: $22,000 USD.
Warranty: Three years parts and labor; 90 days, tubes.
Audio Research Corporation
6655 Wedgwood Lane N., Suite 115
Maple Grove, MN 55311
Phone: (763) 577-9700